The invention relates to a method and to an installation for automatically cutting out pieces of predetermined shapes from a sheet material.
A particular field of application of the invention is that of automatically cutting out pieces from plies of textile material, in particular in the clothing industry. The invention is also applicable to cutting out technical textiles in industrial applications, and to cutting out non-woven materials, such as leather.
A well known method of cutting out pieces from a flexible sheet material consists in bringing the sheet material onto a table in a cutting-out zone, either as a single ply or as a plurality of superposed plies forming a lay-up, and in cutting out pieces in compliance with a pre-established layout by means of a tool which penetrates into the material while the sheet material is held against the table by suction, with a flexible sealing film being applied over the surface of the sheet material. The suction is obtained by sucking through the surface of the table. The tool is a knife moved with vertical vibrating motion or a circular blade and it is displaced relative to the table in a manner such as to cut out the pieces to the desired shapes, and at those locations on the surface of the sheet material which are defined by the pre-established layout. The tool cuts not only through the sheet material but also through the sealing film applied thereagainst.
Downstream from the cutting-out zone lies an unloading zone in which the pieces cut out from the sheet material are recovered. Each piece cut out from a single ply or each stack of pieces (or xe2x80x9cwadxe2x80x9d) cut out from a lay-up underlies a portion of the same shape cut out from the sealing film. The cut-out pieces or wads, optionally still covered with the corresponding portions of sealing film, on which identification information can be placed, are taken off in the unloading zone so as to be directed elsewhere or stored temporarily for subsequent use.
In the unloading zone, the presence of stencil-like xe2x80x9cskeletonsxe2x80x9d of the sheet material and of the sealing film poses various problems. The term xe2x80x9cskeletonsxe2x80x9d is used herein to designate offcuts of the plies or lay-ups of sheet material and of sealing film that are of shape complementary to the shape of the set of cut-out pieces. Such offcuts clutter up the unloading zone and must be removed by an operator. In addition, the presence of offcuts can complicate the identification of the pieces to be unloaded, in particular when at least some of the pieces are difficult to distinguish from the offcuts.
An object of the invention is to remedy the above-mentioned difficulties and, to this end, in one of its aspects, the invention provides a method of automatically cutting up sheet material, the method being of the type comprising bringing at least one ply of sheet material onto a cutting-out table, holding the sheet material against the table by suction, applying a sealing film against the surface of the sheet material, cutting out pieces of predetermined shapes by means of a tool passing through the sealing film and through the sheet material, and removing cut-out pieces downstream from the cutting-out table;
said method being characterized in that at least the xe2x80x9cskeletonxe2x80x9d of the sealing film is diverted from the path of the sheet material in a downstream end zone of the table so as to be recovered automatically, separately from the cut-out pieces.
In a first implementation, at least the skeleton of the sealing film is recovered by automatically winding it back up. The winding back up may be performed on a roll core at a tangential speed which is servo-controlled to the speed at which the sheet material moves over the cutting-out table.
Advantageously, the pieces are cut out while maintaining the structural integrity of the skeleton of the sealing film, so that it is recovered automatically in continuous manner. Optionally, the structural integrity of the skeleton may be re-established by depositing fastenings, e.g. localized fastenings, on the surface of the sealing film.
Thus, the skeleton of the sealing film is absent from the unloading zone, thereby making said zone less littered.
The absence of the skeleton of the film can make it easier to identify the cut-out pieces or wads because they are the only portions of the sheet material that remain covered with sealing film in the unloading zone, providing the skeleton has indeed been separated from the cut-out portions of the sealing film. This separation can made easier by spreading out the sealing film as well as possible so that it is tensioned over the surface of the sheet material during cutting-out.
In a variant of the first implementation of the invention, the sealing film skeleton is removed and recovered with at least some of the cut-out portions of the film. To this end, after cutting out a piece, the link between the cut-out portion of the sealing film and the skeleton may be re-established by means of fastenings deposited or formed on the film in localized manner or in continuous manner along the cutting-out lines. It is then possible to have a sealing film that is partially or fully re-constructed, and that is suitable for re-use.
In a second implementation, fragments of the sealing film constituted by the skeleton and portions of the film that are cut out with the pieces are taken off by being sucked out of the path of the sheet material, and are then removed.
Preferably, the fragments of film are taken off by means of a moving member adjacent to the path of the sheet material. Advantageously, the moving member is rotated by means of it coming into contact with the sheet material and of said sheet material being advanced. In a variant, a rotary moving member may be rotated by means of an optionally-declutchable device associated with independent motorization or moved synchronously with means for moving the sheet material over the table.
Also advantageously, a rotary moving member is used that comprises a plurality of sectors, and suction is established in each sector while said sector is moving from the vicinity of the path of the sheet material and a film fragment removal zone. Positive pressure can then be established in each sector when it reaches the removal zone.
The fragments of film may removed by being deposited in a collector situated above the path of the sheet material, or by being brought to a removal duct.
In another aspect of the invention, the invention provides an installation for automatically cutting up sheet material, and making it possible to implement the above method.
To this end, the invention provides an installation of the type comprising a cutting-out table, a loading station for loading sheet material to be cut-up at an upstream end of the cutting-out table, an unloading station for unloading cut-out pieces at a downstream end of the cutting-out table, suction means for establishing suction at the surface of the cutting-out table, and feed means for bringing a flexible sealing film to the vicinity of the upstream end of the cutting-out table;
in which installation means are further provided for separating at least a xe2x80x9cskeletonxe2x80x9d of sealing film in the vicinity of the downstream end of the cutting-out table and for recovering it automatically outside of the unloading station for unloading the cut-out pieces.
In a first embodiment, the installation further comprises winding-up means for winding up at least the skeleton of the sealing film. The automatic winding-up means may be coupled mechanically to drive means for advancing the sheet material over the cutting-out table, so as to servo-control the tangential winding-up speed to the speed of advance of the sheet material. In a variant, the winding-up means are provided with a motor that is controlled as a function of the speed of advance of the sheet material over the cutting-out table, so as to servo-control the tangential winding-up speed to said speed of advance.
Means for depositing or forming fastenings on the surface of a sealing film present on the cutting-out table may be provided. The means for depositing or forming fastenings are advantageously carried by a carriage that also supports a cutting-out tool. In a variant, the means for depositing or forming fastenings extend transversely relative to the cutting-out table, at the downstream end thereof.
In a second embodiment, the installation further comprises means for taking off fragments of sealing film by suction in the vicinity of the downstream end of the cutting-out table, and means for removing taken-off fragments of film.
Advantageously, the means for taking off fragments of sealing film by suction comprise a rotary drum having a plurality of sectors which communicate with the outside via orifices opening out in the surface of the drum, and means for putting the sectors under suction over a portion of their rotary path between a location situated in the vicinity of the plane of the cutting-out table and a location situated in the vicinity of the means for removing fragments of film.